1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Basic set theory question

  1. Oct 3, 2004 #1
    ok, find the intersection of i=1 to infinitie of A(i).

    A(i) = [0, to 1/i].

    I dont understand what it is asking. what do they mean to find the intersection of that?

    and what if A(i) = [0, 1/n)
  2. jcsd
  3. Oct 3, 2004 #2
    To use mathematicasque notation, Intersect[A(i), {i,1,oo}] is the set of all points in each A(i). There's only one point in all A(i)'s: 0. Therefore the intersection is {0}. Same with the second one. But if they made it (0,1/i) then it would be empty.
  4. Oct 3, 2004 #3
    Do you mean:

    [tex]\bigcap_{i=1}^{\infty} A(i)[/tex]

    where A(i) = [0, 1/i]? Wouldn't the answer be {0}?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook